1. Field of the Invention
The present invention relates to a color filter and more particularly, to a color filter whose light-shielding sections are formed by overlapping two different color layers without using a black matrix, a method of fabricating the color filter, and a Liquid-Crystal Display (LCD) device using the said color filter.
The present invention is applicable to not only LCD devices of various types but also any other devices using a color filter, such as field-emission type display devices, vacuum fluorescent display devices, plasma display devices and image pickup devices.
2. Description of the Related Art
Conventionally, the color filter used for LCD devices comprises colored materials of red (R), blue (B) and green (G) arranged in the respective openings for the pixels to have a predetermined layout (e.g., mosaic, stripe, or delta layout), and a patterned black matrix (which is made of black resin or metal oxide) formed in the light-shielding sections other than the openings. The main reason why the black matrix is used is to raise the contrast, to prevent the mixture among the red, blue, and green colored materials, and to shield the light toward the semiconductor films of the TFTs (Thin-Film Transistors).
With the LCD devices for cellular phones and small-sized LCD devices, essential contrast is not so high. Therefore, no black matrix is used; alternatively, light-shielding sections are formed by partially overlapping the colored materials located in the adjoining openings to realize a light-shielding function similar to that of the black matrix. This is because there is an advantage that the materials, process steps and fabrication cost are reduced since the black matrix is not used.
On the other hand, with the LCD devices for display monitors for personal computers or televisions (TVs), high contrast is essential. Therefore, to omit the black matrix, a structure having an equivalent light-shielding function to that of the black matrix is required. However, if an equivalent light-shielding function to that of the black matrix is obtained by overlapping the colored materials located in the adjoining openings in the typical color filter including colored materials of three primary colors (i.e., red, blue and green), the light-shielding performance of the overlapped parts (stacked parts) of the red and green colored materials is lower than that of the overlapped parts of the other colored materials. This means that the backlight is unable to be shielded sufficiently. For this reason, various ideas have ever been presented and announced to solve this problem.
For example, the Japanese Non-Examined Patent Publication No. 2000-29014 discloses a color filter substrate, which realizes the light-shielding function in the frame area that surrounds the effective display region without the black matrix. With this color filter substrate, three colored layers of red, green and blue are formed in the effective display region and at the same time, two or three of the red, green and blue colored layers are overlapped to form the light-shielding layers in the frame area. In the Publication No. 2000-29014, it is said that the red and blue colored layers are preferably overlapped to realize the light-shielding function. This is because when the red and blue colored layers are overlapped with each other, its transmittance of light can be lowered compared with the areas where the green and blue colored layers are overlapped or the red and green ones are overlapped. In addition, it is said in the Publication No. 2000-29014 that the inter-pixel shielding of light in the effective display region is conducted by overlapping the red and green colored layers, the green and blue colored layers, or the blue and red colored layers (See claims 1 to 2 and FIG. 1).
Therefore, with the color filter substrate of the Publication No. 2000-29014, the inter-pixel light-shielding sections in the effective display region have a two-layer structure of two adjacent ones of the red, blue, and green colored layers. On the other hand, the light-shielding sections in the frame area have a three-layer structure of the red, blue, and green colored layers or a two-layer structure of two adjacent ones thereof.
The Japanese Non-Examined Utility-Model Publication No. 62-181927 discloses a color LCD device, where color images are displayed with three primary colors (i.e., red, green and blue) while the background region is made black. The feature of this device is as follows: Three color filters are provided to realize three primary colors on different surfaces of the substrate and polarizer. One of these color filters is formed on the whole surface for a display color and the two remaining color filters are formed in the background region alone. The background region is made black with a three-layer structure of the three color filters overlapped (See claim 1 and FIG. 1).
With the LCD device of the Publication No. 62-181927, since the background region to be made black is constituted by the three-layer structure of the three primary color filters, the inter-pixel light-shielding sections have a three-layer structure of the said color filters.
The Japanese Patent No. 2590858 (which corresponds to the Japanese Non-Examined Patent Publication No. 63-187277) discloses a color filter, which comprises colored patterns of red, green and blue, and black patterns, all of which are arranged on a transparent support. The black patterns, which are placed in the peripheral area of the screen, are formed by overlapping the three colored layers of red, green and blue, or the two colored layers thereof. The feature of this color filter is as follows: In the boundary and adjacent areas of the respective colored patterns of red, green and blue, the black patterns are formed by overlapping the three colored layers of red, green and blue. On the other hand, in the peripheral area of the screen, the black patterns are formed by overlapping the two colored layers of red and blue (See claim 1 and FIGS. 1 to 4).
Therefore, with the color filter of the U.S. Pat. No. 2,590,858, the inter-pixel light-shielding sections in the display region have a three-layer structure of the red, blue, and green colored layers, and the frame area is formed by a two-layer structure of red and blue colored layers.
The Japanese Non-Examined Patent Publication No. 08-095021 discloses a method of fabricating a color filter, where the black matrix layer is formed by overlapping the transparent colored layers during the process of forming the respective colored layers to obtain a color filter with good flatness. The feature of this method is as follows: The three-layered black matrix layer is formed by using a photomask with half-tone masking regions corresponding to the light-shielding sections at the same time as the formation of the three colored layers of red, green and blue (See claim 1 and FIGS. 1 to 2).
With the color filter fabricated by the method of the Publication No. 08-095021, both the inter-pixel light-shielding sections in the display region and the light-shielding sections in the frame area have a three-layer structure of the red, blue, and green colored layers.
The Japanese Non-Examined Patent Publication No. 2003-014917 discloses three color filters as follows (See claims 1 to 3 and FIGS. 1 to 2).
(i) A first one of the color filters comprises pixels formed and arranged by colored layers on a transparent substrate, where the frame area, which is located in the periphery of the display region, is formed by at least two ones of the colored layers. The feature of this color filter is that the red colored layer has an average transmittance of 1% or less in the wavelength region of 460 to 570 nm.
(ii) A second one of the color filters comprises pixels formed and arranged by colored layers on a transparent substrate, where the frame area is formed by at least two ones of the colored layers. The feature of this color filter is that the blue colored layer has an average transmittance of 1% or less in the wavelength region of 560 to 750 nm.
(iii) A third one of the color filters comprises pixels formed and arranged by colored layers on a transparent substrate, where the frame area is formed by at least two ones of the colored layers. The feature of this color filter is that each of the red and blue colored layers has an average transmittance of 2.5% or less in the wavelength region of 555 to 575 nm.
In the Publication No. 2003-014917, it is said that high OD (Optical Density) values can be obtained by only the stacked or overlapped structure of the colored layers in the frame area and the light-shielding sections opposite to the TFTs. With these filters, the frame area, the inter-pixel light-shielding sections, and the light-shielding sections opposite to the TFTs are formed by a three-layer structure of the red, blue, and green colored layers, or a two-layer structure thereof.
The Japanese Non-Examined Patent Publication No. 2002-082630 discloses two electrooptic devices as follows (See claims 1 to 2 and FIGS. 1 to 2):
(i) A first one of the electrooptic devices comprises TFTs, and light-shielding sections formed by overlapping a first colored layer and a second colored layer, wherein the light-shielding sections are overlapped with at least the channel formation regions of the TFTs.
(ii) A second one of the electrooptic devices comprises pixel electrodes, and light-shielding sections formed by overlapping a first colored layer and a second colored layer, wherein the light-shielding sections are by overlapped with the intervening areas between one of the pixel electrodes and another adjacent thereto.
In the Publication No. 2002-082630, it is said that the first colored layer is preferably blue and the second colored layer is preferably red. With these two electrooptic devices, the light-shielding sections corresponding to the channel formation regions of the TFTs or the inter-pixel light-shielding sections have a two-layer structure formed by two of the red, blue, and green colored layers.
As described above, various ideas have ever been presented and announced to realize sufficient shielding performance of backlight without the black matrix.
By the way, according to the sRGB (standard RGB) or EBU (European Broadcasting Union) standard, required color reproductivity for the display monitors for personal computers and the LCD devices for TV is 72% of the NTSC (National Television System Committee) standard or higher. Therefore, in the case of the combination of a color filter using photosensitive color resists formed by the popular pigment dispersion method and a backlight unit using cold-cathode fluorescent lamps (CCFLs), each of the red, green, and blue color layers has a thickness of 1.8 to 2.0 μm. For this reason, if the whole black matrix is replaced with the three-layered light-shielding sections formed by overlapping the red, green, and blue color layers, the level difference will be 3.6 to 4.0 μm at the maximum in the vicinities of the frame area. Here, the level difference means the difference between the thickness of the pixels (which are formed by one of the red, green, and blue color layers) and the thickness of the light-shielding sections (which are formed by three of the red, green, and blue color layers).
In recent years, there is the growing need to speed the response characteristic of the LCD device up. To answer this need, it is necessary for the cell gap (i.e., the thickness of the liquid-crystal layer) of the LCD panel to be equal to 4.0 μm or lower, preferably, at approximately 3.0 μm. If the cell gap is decreased to such a value, the thickness difference (3.6 to 4.0 μm at the maximum), i.e., the level difference between the pixels and the light-shielding sections, will be greater than the cell gap (3.0 μm or less). Thus, with the color filters for the display monitors for personal computers and the LCD devices for TV that necessitates high-speed response characteristics, the light-shielding sections are unable to be formed by the layered structure of the three color layers. This means that the light-shielding sections need to be formed by the layered structure of the two color layers.
FIGS. 1A, 1B and 1C show an example of the prior-art color filters used for the LCD devices of this type, where the light-shielding sections are formed by two different color layers overlapped. FIG. 1A is an explanatory partial plan view showing the pattern of the red color layer used in this color filter, FIG. 1B is an explanatory partial plan view showing the pattern of the blue color layer thereof, and FIG. 1C is an explanatory partial plan view showing the pattern of the green color layer thereof. FIG. 2 is an explanatory partial plan view of the prior-art color filter constituted by the red, blue and green color layers shown in FIGS. 1A, 1B, and 1C.
The red color layer 101 used for this prior-art color filter is formed on a surface (X-Y plane) of a transparent glass plate (not shown). The layer 101 comprises stripe-shaped red pixel formation sections 101R and connection sections 101L, as shown in FIG. 1A.
The stripe-shaped red pixel formation sections 101R are extended along the Y direction (vertical direction in FIG. 1A) and arranged along the X direction (horizontal direction in FIG. 1A) at predetermined intervals. The sections 101R are used for forming rectangular red pixels arranged in the Y direction at predetermined intervals. Thus, it may be said that each of the sections 101R is formed by red pixels and red inter-pixel parts that interconnect the adjoining red pixels.
The connection sections 101L interconnect the adjoining red pixel formation sections 101R. Moreover, the connection sections 101L define rectangular blue pixel windows 101B arranged along the Y direction at predetermined intervals and rectangular green pixel windows 101G arranged along the Y direction at predetermined intervals. Each of the blue pixel windows 101B is located at a position where a blue pixel is to be formed. Each of the green pixel windows 101G is located at a position where a green pixel is to be formed.
Accordingly, the red pixels are aligned along the Y direction at predetermined intervals. The green pixels are aligned along the Y direction at the same intervals as the red pixels in such a way as to be adjacent to the red pixels. The blue pixels are aligned along the Y direction at the same intervals as the red pixels in such a way as to be adjacent to the green pixels. This layout or arrangement of the red, green and blue pixels thus aligned is repeatedly aligned along the X direction.
The blue color layer 102 used for the prior-art color filter of FIGS. 1A to 1C is formed on the surface of the glass plate to be overlapped with the red color layer 101. The layer 102 comprises stripe-shaped blue pixel formation sections 102B and connection sections 102L, as shown in FIG. 1B.
The stripe-shaped blue pixel formation sections 102B are extended along the Y direction and arranged along the X direction at predetermined intervals. The sections 102B, which are located on such positions as to be superposed on the corresponding blue pixel windows 101B of the red color layer 101, are used for forming rectangular blue pixels arranged in the Y direction at predetermined intervals. Thus, it may be said that each of the sections 102B is formed by blue pixels and blue inter-pixel parts that interconnect the adjoining blue pixels.
The connection sections 102L interconnect the adjoining blue pixel formation sections 102B. Moreover, the connection sections 102L define rectangular red pixel windows 102R arranged along the Y direction at predetermined intervals and rectangular green pixel windows 102G arranged along the Y direction at predetermined intervals. Each of the red pixel windows 102R is located at a position where a red pixel is to be formed. Each of the green pixel windows 102G is located at a position where a green pixel is to be formed.
Accordingly, the red pixel windows 102R are located at such positions as to be superposed on the corresponding red pixel formation sections 101R of the red color layer 101. The green pixel windows 102G are located at such positions as to be superposed on the corresponding green pixel windows 101G of the red color layer 101.
The green color layer 103 used for the prior-art color filter of FIGS. 1A to 1C is formed on the surface of the glass plate to be overlapped with the red and blue color layers 101 and 102. The layer 103 comprises stripe-shaped green pixel formation sections 103G, as shown in FIG. 1C. Unlike the red and blue color layers 101 and 102, the green color layer 103 does not have connection sections like the connection sections 101L and 102L.
The stripe-shaped green pixel formation sections 103G are extended along the Y direction and arranged along the X direction at predetermined intervals. The sections 103G, which are located on such positions as to be superposed on the corresponding green pixel windows 101G of the red color layer 101 and the corresponding green pixel windows 102G of the blue color layer 102, are used for forming rectangular green pixels arranged in the Y direction at predetermined intervals. Thus, it may be said that each of the sections 103G is made of green pixels and green inter-pixel parts that interconnect the adjoining green pixels.
The above-described prior-art color filter of FIGS. 1A to 1C, which is fabricated by overlapping the red, blue, and green color layers 101, 102, and 103 with the above-described patterns in this order, has the structure as shown in FIG. 2.
As seen from FIG. 2, the stripe-shaped red pixel formation sections 101R of the red color layer 101 are overlapped with the corresponding red pixel windows 102R of the blue color layer 102, thereby defining the red pixels. This means that the exposed parts of the red pixel formation sections 101R from the corresponding red pixel windows 102R form the red pixels.
Similarly, the stripe-shaped blue pixel formation sections 102B of the blue color layer 102 are overlapped with the corresponding blue pixel windows 102B of the red color layer 101, thereby defining the blue pixels. This means that the parts of the blue pixel formation sections 102B located inside the corresponding blue pixel windows 102B form the blue pixels.
The stripe-shaped green pixel formation sections 103G of the green color layer 103 are overlapped with the corresponding green pixel windows 101G of the red color layer 101 and the corresponding green pixel windows 102G of the blue color layer 102, thereby defining the green pixels. This means that the parts of the green pixel formation sections 103G located inside the overlapped, corresponding green pixel windows 101G and 102G form the blue pixels.
The red inter-pixel parts of the stripe-shaped red pixel formation sections 101R of the red color layer 101 are overlapped with the corresponding connection sections 102L of the blue layer 102 or the corresponding blue inter-pixel parts of the stripe-shaped blue pixel formation sections 102B thereof, thereby forming two-layer-structured light-shielding sections. These light-shielding sections, which have the two-layer structure formed by overlapping the red and blue color layers 101 and 102, have the same pattern as the black matrix. However, the green inter-pixel parts of the green color layer 103 are overlapped with both the corresponding connection sections 101L of the red color layer 101 and the corresponding connection sections 102L of the blue color layer 102. Therefore, the light-shielding sections located at these positions have the three-layer structure of the red, blue and green color layers 101, 102 and 103.
The cross-sectional structure along the IIIA-IIIA line of FIG. 2 (i.e., the cross-sectional structure of the part including the green pixel formation section 103G) is shown in FIG. 3A. As shown in FIG. 3A, the red, blue and green color layers 101, 102 and 103 are overlapped in this order on the surface of the glass plate 109. An overcoat layer 123 is formed on the green color layer 103. At the positions located over the three-layered light-shielding sections 133 (which are disposed right over the corresponding green inter-pixel parts of the green color layer 103), photo spacers 120 are formed on the overcoat layer 123. These photo spacers 120 are formed by patterning a known photoresist (photosensitive resin) film.
As clearly seen from FIG. 3A, the light-shielding section 133 has the three-layer structure formed by overlapping the red, blue, and green color layers 101, 102 and 103. The photo spacers 120 are formed on the overcoat layer 123 that covers the color layers 101, 102 and 103. Thus, there is a level difference “h” between the green pixel formed by the green color layer 103 (i.e., the green pixel formation section 103G) and the adjoining light-shielding section 133 thereto, where the level difference “h” is approximately equal to the sum of the thicknesses of the red and blue color layers 101 and 102.
The widths of the blue inter-pixel parts of the blue color layer 102 and the connection sections 102L thereof are slightly larger than the widths of the red inter-pixel parts of the red color layer 101 and the connection sections 101L thereof. Therefore, as shown in FIG. 3A, the both edges of the blue inter-pixel parts of the blue color layer 102 and the connection sections 102L thereof, which are placed on the red inter-pixel parts of the red color layer 101 or the connection sections 101L thereof, are contacted with the surface of the glass plate 109.
The state where a TFT substrate 126 is coupled with the color filter with the structure of FIG. 3A is shown in FIG. 3B. In this state, as clearly seen from FIG. 3A, the cell gap “c” is equal to the sum of the level difference “h” and the height of the photo spacers 120.
FIG. 4A shows the state where the positions of the photo spacers 120 are changed to those located over the blue color layer 102 in the above-described prior-art color filter of FIG. 2. The cross-sectional structure along the VA-VA line in FIG. 4A (i.e., the cross-sectional structure of the part including the blue pixel formation section 102B of the layer 102) is shown in FIG. 5A.
At the positions shown in FIG. 5A, the light-shielding sections 133a have the two-layer structure comprising the red and blue color layers 101 and 102. Thus, the level difference “i” between the blue pixels and the light-shielding sections 133a adjoining thereto is approximately equal to the thickness of the red color layer 101. The level difference “i” is smaller than the level difference “h” (see FIGS. 3A and 3B) between the green pixels and the light-shielding sections 133 adjoining thereto by the thickness of the green color layer 103.
The state where the TFT substrate 126 is coupled with the color filter of FIG. 4A is shown in FIG. 5B. In this state, as clearly seen from FIG. 5B, the cell gap “c” is equal to the sum of the level difference “i” and the height of the photo spacers 120. However, the level difference “i” is smaller than the level difference “h”. Therefore, the height of the photo spacers 120 can be increased by the gap between the differences “h” and “i”.
The cross-sectional structure along the VIA-VIA line of FIG. 4A (i.e., the cross-sectional structure of the part including the green pixel formation section 103G) is shown in FIG. 6A. This structure is the same as that of FIG. 3A except that the photo spacers 120 do not exist. Therefore, the level difference “j” of FIG. 6A is the same as much as the level difference “h” of FIG. 3A. The state where the TFT substrate 126 is coupled with the structure of FIG. 6A is shown in FIG. 6B. In this case, if the cell gap “c” is set to be equal to that of FIG. 5B, the gap “e” over the light-shielding sections 133 is equal to the subtraction result of the level difference “j” from the cell gap “c”. Accordingly, the gap “e” is considerably smaller than the gap over the light-shielding sections 133a (which is equal to the height of the photo spacers 120).
In this way, when the photo spacers 120 are placed on the green pixel formation sections 103G (see FIG. 2), the level difference “h” will be large. Thus, to obtain a desired value of the cell gap “c”, the height of the photo spacers 120 needs to be decreased. Since the gap “e” over the light-shielding sections 133 is equal to the height of the photo spacers 120, the gap “e” is decreased by the decreased height of the photo spacers 120. On the other hand, when the photo spacers 120 are placed on the blue pixel formation sections 102B (see FIG. 4A), the level difference “i” between the blue pixels and the light-shielding sections 133a is smaller than the level difference “h” between the green pixels and the light-shielding sections 133 (i.e., i<h). Accordingly, the gap “e” over the light-shielding sections 133 can be increased by increasing the height of the photo spacers 120.
In addition, the photo spacers 120 may be formed at the positions over the red pixel formation sections 101R, as shown in FIG. 4B. In this case, the cross-sectional structure is the same as that of the case where the photo spacers 120 are located over the blue pixel formation sections 120B (see FIG. 5A). Therefore, the explanation about it is omitted here.
As the TFT substrate 126, for example, a TFT substrate of the IPS (In-Plane Switching) type having the structure of FIG. 7 may be used. This structure is approximately the same as that illustrated in FIG. 6 of the Japanese Non-Examined Patent Publication No. 2005-241923. FIG. 7 shows the structure in one of the pixel regions.
As shown in FIG. 7, the TFT substrate 126 comprises a common electrode line 143 made of metal, a contact hole 145 for a common electrode, a transparent common electrode 146, a transparent pixel electrode 147, a contact hole 148 for the pixel electrode 147, a scanning line 149, a data line 150, a TFT 151, a source electrode 152 of the TFT 151, a drain electrode 153 of the TFT 151, an island-shaped amorphous silicon (a-Si) film 154 for forming an active layer of the TFT 151, and a pixel auxiliary electrode 156.
The pixel electrode 147 has three zigzag-shaped comb teeth. The common electrode 146 has four zigzag-shaped comb teeth. The pixel electrode 147 and the common electrode 146 are arranged in such a way as to be alternately engaged with each other in the region surrounded by the adjoining scanning lines 149 and the adjoining data lines 150. The two teeth of the common electrode 146 at its each side are overlapped with the corresponding data lines 150, respectively. The pixel auxiliary electrode 156 has one comb tooth superposed on the central tooth of the pixel electrode 147.
Each of the data lines 150 is electrically connected to the drain electrode 153 of a corresponding one of the TFTs 151. Each of the scanning lines 149 is electrically connected to the gate electrode (not shown) of a corresponding one of the TFTs 151. Each of the pixel electrodes 147 is electrically connected to the source electrode 152 of a corresponding one of the TFTs 151 by way of a corresponding one of the contact holes 148. Each of the common electrodes 146 is electrically connected to a corresponding one of the common electrode lines 143 by way of a corresponding one of the contact holes 145.
The above-described prior-art color filter shown in FIGS. 1 to 6 has the three problems explained below.
The first problem is that the level difference “h” (see FIGS. 3A and 3B) between the green pixels and the adjoining three-layered light-shielding sections 133 thereto is so large that the freedom of designing the cell gap “c” may be damaged.
Specifically, the level difference “h” between the green pixels and the light-shielding sections 133, which varies dependent on the width of the said sections 133, is likely to be excessively large. In the case of the thickness of the overlapped parts of the red and green color layers 101 and 103 being set at 70 to 90% (these values are determined in consideration of the thickness averaging due to flow during the coating process of the resist for each color) of the thickness of the red pixel formation sections 101R and that of the green pixel formation sections 103G, supposing that the red pixel formation sections 101R are 2.0 μm in thickness, the blue pixel formation sections 102B are 2.0 μm in thickness, the green pixel formation sections 103G are 2.0 μm in thickness, and the overcoat layer 123 is 1.0 μm in thickness, the overall thickness of the light-shielding sections 133 will be approximately 5 μm to approximately 6 μm while the overall thickness of the respective pixel formation sections will be 3.0 μm. (At this time, the overcoat layer 123 will be considerably thin, although it depends on the viscosity.) This means that the level difference “h” will be approximately 2.0 μm to approximately 3.0 μm, which is extremely large. For example, if the height difference “h” is 3.0 μm, the cell gap “c” over the green pixel is difficult to be set at 3.0 μm or less, which means that that the freedom of designing the cell gap “c” is damaged vastly.
To reduce the level difference “h”, the parts of the green color layer 103 (i.e., the green inter-pixel parts of the green pixel formation sections 103G) that form the three-layered light-shielding sections 133 may be selectively removed by polishing. However, the green pixel formation sections 103G of the green color layer 103 are arranged on the almost entire surfaces of the corresponding light-shielding sections 133, and the total area of the green color layer 103 to be polished and removed is very wide. Therefore, even if a polishing machine is used to polish the entire surface of the said color filter, the said parts are difficult to be removed. Moreover, since such the polishing operation necessitates a long time, the tact time increases extensively and the mass productivity is damaged.
The second problem is that local gap defects are likely to occur due to plastic deformation or breakdown of the photo spacers 120 and that the color layers are difficult to be thickened to raise the color reproductivity.
Specifically, when the cell gap “c” is constant, the height of the photo spacers 120 is determined by the level difference “h” between the green pixels and the three-layered light-shielding sections 133. The level difference “h” is approximately equal to the sum of the thicknesses of the red and blue color layers 101 and 102. Therefore, thickening the red and blue color layers 101 and 102 to raise the color reproductivity leads to the increase of the level difference “h” and the height decrease of the photo spacers 120. Accordingly, it is difficult to raise the color reproductivity by thickening the red and blue color layers 101 and 102 (and the green color layer 103).
Moreover, the amount of possible elastic deformation of the photo spacers 120 decreases as their height decreases. Thus, the more the height of the spacers 120 is reduced due to the increase of the difference “h”, the less the deformation margin of the spacers 120 against the local pressure stress applied to the display surface from the outside of the LCD panel. As a result, local gap defects are likely to occur due to plastic deformation or breakdown of the photo spacers 120.
The third problem is that the two-layered light-shielding sections 133a in the effective display region do not utilize effectively the operation characteristics in the normally black mode of the IPS or VA (Vertically Aligned) type LCD device and the light-shielding effect for the backlight with the metal lines on the TFT substrate 126.
Specifically, with the above-described prior-art color filter of FIGS. 1A to 6B, the two-layered light-shielding sections 133a comprising the red and blue color layers 101 and 102 (where the OD value is maximized) are placed in not only the region where a high OD value is necessary but also the region where an OD value may be low. Therefore, the three-layered light-shielding sections 133 comprising the red, blue and green color layers 101, 102 and 103 are formed at the positions adjacent to the green pixels. As a result, the cell gap “c” has to be determined in conformity with the large level difference “h” between the green pixels and the light-shielding sections 133. For this reason, the gap “e” (see FIG. 6B) between the three-layered light-shielding sections 133 and the TFT substrate 126 may be very narrow if the cell gap “c” is set at particular values. This means that a problem that foreign objects are likely to be caught in the narrowed gap “e” occurs. This is because if foreign objects are caught in the narrowed gap “e”, gap defect will be generated in the light-shielding sections 133, which gives bad effects to the display quality.